In the chemical processing by many types of apparatus, such as in etching systems, the articles to be treated are subject to an etching process, often generally followed by a washing process. Similarly, as part of an etching system, a masking process may be utilized, which will also be generally followed by a washing process. Where etching is done, it will often be accomplished by treating unmasked portions of printed circuit boards or the like with an acid such as ferric chloride or the like. For purposes of this invention, all acids, resists, rinse waters or other solutions will be encompassed within the term "liquid," although most generally the liquid to be removed from and dryed from the articles will comprise water, in whole or in part.
Also, in accordance with the broad aspects of this invention, while the apparatus is particularly adaptable for drying printed circuit boards and like elements, other elements, such as printed circuit film, and even articles that are not related to printed circuit boards may be dried in accordance with an apparatus as described herein.
In accordance with the prior art, it is known to pass articles being treated through a chamber on a conveyor mechanism, and to utilize air knives as a form of gas knife means, in order to blow or impel liquid from the articles. An example of this is taught in U.S. Pat. No. 3,801,387, and to some extent in the art cited therein.
It is also known in the art to dry by blowing air taken from the environment of the room in which the apparatus is located, through three pairs of air knives, for the purpose of chasing water off the surface of the article. This yields an article that to appearances is dry, but does contain condensed moisture because of the ambient air in the room, which may have been very close to the dew point. Dryers of this prior art type are therefore limited such that the effectiveness of drying is dependent upon the relative humidity of the ambient air that is fed to the air knives. Thus, the effectiveness of a dryer can vary depending upon its location geographically, weather conditions at any given time of the year, and various other factors that can affect the relative humidity in the environment of utilization of the apparatus.